I had extracted RaceTypes.yaml. If you want to play modified race is multiplayer, then everyone in mulpliplayer game should have this file, situated in ".....Master of Orion\MasterOfOrion_Data\GameplayData", and he should be the same for all.

I don't know yet how to share this file, I hope, you tell me and I'll share. But.

Untill developers implemented customized races in PvP I invited you make our own ballanced races. It's just the beginning of our discussion, ofc nothing stops you to make your own mods each game.